CPS chief Alison Saunders “did not sufficiently recognise the extent and seriousness” of failures within the disclosure process”, according to a Commons’ justice committee report.
It said there had been “insufficient focus and leadership” over the issue – but Ms Saunders said tackling the problem was now her “top priority”.
Committee chairman Bob Neill said some people had been sent to prison after evidence was not handed over to defence lawyers by police and prosecutors.
“This is not acceptable,” said the Tory MP and barrister.
“As we’ve seen in high profile cases since last year – disclosure failings are extremely damaging for those concerned and can have a permanent life-long impact.
“These failings have caused miscarriages of justice and – as the director of public prosecutions even admitted to us – some people have gone to prison as a result.”
The Crown Prosecution Service and police must hand over material that helps the defence but this is often viewed as an “administrative headache”, said Mr Neill.
A series of rape trials collapsed in 2017 when it became clear that vital evidence had not been properly handed over.
Samuel Armstrong, who was chief of staff for a Tory MP, said at the time that his “whole life had been turned upside down”.
He said his defence had only received “crucial evidence” eight days before the start of the trial. He was then found not guilty.
That evidence is believed to have been messages from his accuser’s phone that showed she had contacted a journalist hours after the alleged assault to get a “sympathetic” portrayal.
Her medical notes also contained details of a history of mental health issues, including depression and anxiety.
Liam Allan also told Sky News how he spent two years living in fear after a rape claim was made against him.
His case was also thrown out of court after it emerged a detective had failed to hand over text messages on the accuser’s phone – seriously undermining the case.
“While the police are trying to prove the accuser’s word, no one is really out looking for evidence to support what you’re saying,” he said.
The collapsed cases led to a review of all live rape and sexual assault prosecutions in England and Wales, with disclosure problems found in 47.
The justice committee report says diclosure must be seen as a “core justice duty” rather than an “administrative add-on”.
A National Disclosure Improvement Plan is being brought in as part of a review by the attorney general.
“The proliferation of electronic evidence makes disclosure ever more challenging, and we need the right skills, technology, resources and guidelines, to resolve this once and for all,” said Mr Neill.
He said the improvement plan “must deliver” and that “too many reviews of disclosure that have not resulted in real change”.
Alison Saunders said: “I have been very clear that addressing the long-standing problems in managing disclosure across the criminal justice system is my top priority.”
She said there was now an “unprecedented focus on finding solutions” and changing “the wider culture within the CPS and policing”.